linux-kernel - [PATCH] misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge

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Date:   Mon, 26 Apr 2021 18:07:27 -0400
From:   Tong Zhang <ztong0001@...il.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tong Zhang <ztong0001@...il.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge

the PCI bridge might be NULL, so we'd better check before use it

[    1.246492] BUG: kernel NULL pointer dereference, address: 00000000000000c0
[    1.248731] RIP: 0010:pci_read_config_byte+0x5/0x40
[    1.253998] Call Trace:
[    1.254131]  ? alcor_pci_find_cap_offset.isra.0+0x3a/0x100 [alcor_pci]
[    1.254476]  alcor_pci_probe+0x169/0x2d5 [alcor_pci]

Signed-off-by: Tong Zhang <ztong0001@...il.com>
---
 drivers/misc/cardreader/alcor_pci.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/misc/cardreader/alcor_pci.c b/drivers/misc/cardreader/alcor_pci.c
index cd402c89189e..1c33453fd5c7 100644
--- a/drivers/misc/cardreader/alcor_pci.c
+++ b/drivers/misc/cardreader/alcor_pci.c
@@ -102,6 +102,9 @@ static int alcor_pci_find_cap_offset(struct alcor_pci_priv *priv,
 	u8 val8;
 	u32 val32;
 
+	if (!pci)
+		return 0;
+
 	where = ALCOR_CAP_START_OFFSET;
 	pci_read_config_byte(pci, where, &val8);
 	if (!val8)
-- 
2.25.1